Integral field observations of the blue compact galaxy Haro14 - Star formation and feedback in dwarf galaxies

摘要

Context. Low-luminosity, gas-rich blue compact galaxies (BCG) are ideal laboratories to investigate the triggering and propagation of star formation in galaxies, the effects of massive stellar feedback within a shallow gravitational potential, and the enrichment of the interstellar medium. Aims. We aim to probe the morphology, stellar content, and kinematics, along with the nebular excitation and ionization mechanism, in the BCG Haro?14 by means of integral field observations. Methods. We observed Haro?14 at the Very Large Telescope, working with the Visible Multi-Object Spectrograph. From these data we build maps in continuum and in the brighter emission lines, produce line-ratio maps (interstellar extinction, density, and diagnostic-line ratios), and obtain the velocity and velocity dispersion fields. We also generate the integrated spectrum of the major H? ii regions and young stellar clusters identified in the maps to determine reliable physical parameters and oxygen abundances. Results. We find as follows: i) the current star formation in Haro?14 is spatially extended with the major H? ii regions placed along a linear (chain-like) structure, elongated in the north-south direction, and in a horseshoe-like curvilinear feature that extends about 760 pc eastward; the continuum emission is more concentrated and peaks close to the galaxy center; ii) two different episodes of star formation are present in the central galaxy regions: the recent starburst, with ages ≤ 6 Myr and the intermediate-age clusters, with ages between 10 and 30 Myr; these stellar components rest on a several Gyr old underlying host galaxy; iii) the H α /H β pattern is inhomogeneous, with excess color values varying from E ( B ? V ) = 0.04 up to E ( B ? V ) = 1.09 ; iv) shocks play a significant role in the galaxy; and v) the velocity field displays a complicated pattern with regions of material moving toward us in the east and north galaxy areas. Conclusions. The morphology of Haro?14, its irregular velocity field, and the presence of shocks speak in favor of a scenario of triggered star formation. Ages of the knots, i.e., 6 Myr for the starburst and 10 ? 30 Myr for the central clusters, are consistent with the ongoing burst being triggered by the collective action of stellar winds and supernovae originated in the central clusters.